1. Field of the Invention
The present invention relates to an electronic cartridge which has a heat sink.
2. Background Information
FIG. 1 shows a product marketed by Intel Corporation, the assignee of this application, which is referred to as a single edge contact cartridge (SECC). The Intel SECC includes a microprocessor which is assembled into a package 1 that is mounted to a substrate 2. The SECC may also have other integrated circuit packages 3 which contain static random access memory (SRAM) integrated circuits.
One edge of the substrate 2 has a plurality of conductive pads 4 which can be inserted into an electrical connector 5. The electrical connector 5 can be mounted to a printed circuit board 6 such as the motherboard of a computer. The pads 4 and connector 5 electrically couple the substrate 2 to the circuit board 6.
The substrate 2 and integrated circuit packages 1 and 3 are enclosed by a cover 7 and a thermal plate 8. The cover 7, plate 8 and substrate 2 provide an electronic cartridge which can be plugged into a computer.
The electrical system shown in FIG. 1 can be subjected to external shock and vibration loads. Such loads may produce intermittent separation between the pads 4 and the connector 5. Intermittent separation between the pads 4 and connector 5 may create electrical "opens." The system is provided with a retention mechanism 9 to secure the substrate 3 to the connector 5 and prevent contact separation under shock and vibration loads.
The retention mechanism 9 includes a pair of guide rails 10 that are mounted to the circuit board 6. Each rail 10 includes an aperture 11 which receives a latch 12 that extends from the cover 7 of the cartridge. When inserted into the aperture 11 each latch 12 prevents the substrate 2 from being pulled out of the connector 5. The substrate 2 can be unplugged from the connector 5 by pressing a pair of latch levers 13 and pulling the cartridge away from the board 6. Pressing the levers 13 moves the latches 12 out of the apertures 11 of the rails 10.
The integrated circuits generate heat which must be removed from the circuits. The thermal plate 8 is thermally coupled to the integrated circuit package 1 of the SECC to provide a thermal path for the heat generated by the microprocessor. A heat sink 14 may be mounted to the thermal plate 8 to further facilitate the removal of heat.
As shown in FIG. 2, the thermal plate 8 is in direct thermal contact with the package 1 that contains the microprocessor so that heat can flow from the package 1, through the plate 8, and into the heat sink 14. The package 1 typically incorporates a heat slug 15 which makes the package taller than the SRAM packages 3. Consequently, there is an air gap 16 between the SRAM packages 3 and the thermal plate 8. Air is a thermal insulator. Therefore, heat generated by the SRAM devices primarily flows into the substrate which is a relatively inefficient means of removing heat from the packages 3.
A heat slug (not shown) can be attached to the heat sink 14 to fill the air gap 16 and provide a direct thermal path between the SRAM packages 3 and the sink 14. Attaching a heat slug to the heat sink 14 increase the complexity and cost of producing the assembly. It would be desirable to provide a cost effective heat sink design that will allow heat to be removed from the top surface of the SRAM packages 3.